on which database is Ninox build

https://ninoxdb.de/en/forum/technical-help-5ab8fe445fe2b42b7dd39ee7/what-is-the-language-5bb3daa9a9ece4783d4d6b10

If you look at this link https://ninox.com/en/jobs/senior-full-stack-developer in their Careers section, you'll see Mongodb and PostgreSQL mentioned. I'm just speculating, but I would say Mongodb because of the lack of SQL JOIN commands in their "custom" lanquage.